PORT-AU-PRINCE, Haiti - Rain and wind gusts from the outer bands of Tropical Storm Emily struck Puerto Rico on Tuesday as the storm gathered strength on a track that threatened the Dominican Republic and Haiti, where more than 630,000 people are still without shelter after last year's earthquake.

Puerto Rico was spared major damage and forecasters said Emily was headed next to the more vulnerable island of Hispaniola, which is shared by Haiti and the Dominican Republic, where rains from the front of the storm should start arriving in force Wednesday afternoon.

"The biggest threat to lives is probably the flooding," said John Dlugoenski, senior meteorologist with Accuweather.com.

Dlugoenski said a "steady shield of rain" would reach the Dominican Republic and then Haiti around noon Wednesday, and the rainfall would worsen late afternoon, early evening. Skies would likely clear up Thursday afternoon.

On Puerto Rico, there were no reports of major damage or injuries and no immediate demand for the nearly 400 schools that were converted into emergency shelters around the island. Emily had been expected to bring up to 6 inches (15 centimeters) to the island.

Gov. Luis Fortuno declared a state of emergency and most government offices were closed. Ahead of the storm, people cleared water and other emergency supplies from store shelves and tourists fled the small Puerto Rican islands of Culebra and Vieques.

Most of the island saw no more than sporadic gusts and showers. But the National Weather Service said up to 5 inches of rain had fallen in the Cabo Rojo-Mayaguez region in the island's west.

One regional airline, LIAT, canceled flights but otherwise activity was normal at the airport and throughout most of the capital.

The U.S. National Hurricane Center said the storm, which had been almost stationary in the morning, was on a west track at 14 mph by night. The path would bring Emily's center over Hispaniola by Wednesday afternoon or Thursday. Both countries, but especially Haiti, are prone to devastating floods.

A slow-moving storm that triggered mudslides and floods in Haiti killed at least 28 people died in June.

Late Tuesday night, the storm was about 165 miles south of San Juan, Puerto Rico. It had maximum sustained winds of 50 mph. Dlugoenski said the wind speed was unlikely to accelerate as the storm passed over land but flooding and mudslides still posed the bigger threat to Hispaniola.

Civil defense officials and the military in the Dominican Republic have already begun moving people out of high-risk zones ahead of the storm. Haitian authorities urged people to conserve food and safeguard their belongings.

In Haiti's capital of Port-au-Prince, Jislaine Jean-Julien, a 37-year-old street merchant displaced by the January 2010 earthquake, said she was praying the storm would pass her flimsy tent without knocking it over.

"For now, God is the only savior for me," Jean-Julien said at the edge of a crowded encampment facing the quake-destroyed National Palace. "I would go some place else if I could but I have no place else to go."

Haitian emergency authorities set aside a fleet of 22 large white buses in the event they needed to evacuate people from flooded areas. Emergency workers would then bus the people to dozens of schools, churches and other buildings that will serve as shelters.

"We're working day and night to be to able respond quickly in case we have any disasters," said Marie Alta Jean-Baptiste, director of Haiti's Civil Protection Agency.

Emergency workers, both Haitian and foreign, also sent out text messages to cellphone users, alerting them to the approaching storm and to take precautions such as staying with friends or relatives if that were an option.

Such advisories are not uncommon but few in Haiti have the means to heed them because of the crushing poverty.

"This is not the first time we've heard these messages," said Alexis Boucher, a 29-year-old man who lives in Place Boyer, a public square that became a camp after the earthquake. "We receive these messages and yet we still don't have anywhere to go."

The United Nations peacekeeping force in Haiti notified its 11,500 troops to be on standby in case they need to respond, said Sylvie Van Den Wildenberg, a spokeswoman for the U.N. peacekeeping mission. The International Federation of Red Cross and Red Crescent Societies, too, put emergency teams on standby, who have access to relief supplies already in place for up to 125,000 people in seaside towns throughout the country.

In the Dominican Republic's southern tourist districts, workers at hotels and restaurants gathered up umbrellas, tables, chairs, and anything else that might be blown away.

Capt. Frank Castillo, dock master of the Marina Casa de Campo in the southeastern tourist city of La Romana, and his crew helped boat owners secure their vessels in slips or pull them ashore.

In the U.S. Virgin Islands, the government said it would not open emergency shelters on Tuesday afternoon since storm tracking information indicated that the U.S. territory would not get hit by damaging winds or heavy rainfall.

So far, the storm had not caused major problems passing through the Caribbean, just minor ones. It forced the postponement until the weekend of the annual Carnival parade and caused mudslides and local flooding in Dominica.

A tropical storm warning was in effect for Puerto Rico, Vieques, Culebra, the Dominican Republic and Haiti. A tropical storm watch was in effect for the U.S. Virgin Islands, the southeast Bahamas, and the Turks and Caicos Islands.